Now to Syria, where earlier this week it marked six years of conflict. First, let's talk about one act in particular. The U.S. conducted an airstrike in a rebel-held part of northern Syria yesterday, leveling a building next to a mosque. Dozens of people were killed.

The Pentagon says the military targeted a meeting of senior al-Qaida leaders. Syrians on the ground tell a different story. They say it was a regular meeting of a local group. And most of the people killed were civilians. NPR's Alice Fordham joins us now from Beirut. And, Alice, tell us more about what you know about what happened.

ALICE FORDHAM, BYLINE: The strike happened yesterday evening about 7 p.m. Now, what it hit was a building that was part of a small compound of structures that also includes another building that's a mosque. Low estimates of the death toll place it above 30 people, high estimates more than 50 people. Now, what the United States says is that they are confident that the building that they hit was being used by al-Qaida for a meeting with probably dozens of people attending. If you look at photographs and videos of the scene, a huge crater is all that's left of the building that was targeted.

But the Syrian Observatory for Human Rights, which is a monitor, they insist this wasn't an al-Qaida meeting. They say it was a peaceful religious group. Some activists in the local area tell us that a group meets there every week and has done so for six months or maybe longer. It's not ruled out that it could have been local people meeting and a senior al-Qaida leader attended the meeting that night.

CORNISH: What's the history here? Does al-Qaida have a significant presence in this area?

FORDHAM: Yes, they do. And it has been growing stronger. So, Audie, what's been happening in northern Syria as you know is that in the last few months, the rebels there have lost a lot of their territory, notably in the city of Aleppo. So the opposition and their supporters are now crowded into shrinking territory, mostly rural areas like where this village, where this mosque is. And what you might call the moderate opposition has become weaker and more fractured, while groups with links to al-Qaida have consolidated, recruited, formed coalitions.

It's left people with few options - civilians, armed groups. They've been left with few options but to be co-opted or at least not oppose the growing influence of al-Qaida. And although, you know, of course there's a lot of focus on the fight against another extremist group, ISIS, in Syria. The United States has also been conducting strikes for years designed to weaken the al-Qaida presence there.

CORNISH: Have those al-Qaida-linked groups said anything about this attack?

FORDHAM: Not yet. And the Pentagon also hasn't identified exactly who they say they struck. And typically in such cases, this takes a few days or weeks to come out.

CORNISH: Now, President Trump has been very critical of the military strategy held by President Barack Obama. Does a strike like this represent a real change in tactics for the U.S.?

FORDHAM: Well, we do have to remember, as I say, there have been strikes by the U.S. on al-Qaida in Syria for years. But Pentagon officials have told NPR that the nature of this strike on a mosque compound - which is a civilian target - hitting dozens of people is something that would have been unlikely to be approved when Obama was in the White House.